Abstract: We report here on a recent lattice study of the QCD transition region atfinite temperature and zero chemical potential using domain wall fermionsDWF. We also present a parameterization of the QCD equation of state obtainedfrom lattice QCD that is suitable for use in hydrodynamics studies of heavy ioncollisions. Finally, we show preliminary results from a multi-stagehydrodynamics-hadron cascade model of a heavy ion collision, in an attempt tounderstand how well the experimental data e.g. particle spectra, ellipticflow, and HBT radii can constrain the inputs e.g. initial temperature,freezeout temperature, shear viscosity, equation of state of the theoreticalmodel.